This invention relates to a coupling or clutch embodying a construction of parts to prevent an overload to the transmission of torque in a drive train. More particularly, the present invention relates to such a clutch or coupling of a detent-type wherein plungers are slideably supported in a housing part to engage with seats in a hub part under the force of spring-biased pull pins supported by the hub part to deliver a resilient force to the drive plungers via a pressure plate. When desired, axial floating between machine elements can be accommodated by sliding movement between the housing and hub of the clutch or coupling as well as a geared phase adjustment between the housing and hub.
Various designs of a clutch or coupling used for an overload torque-limiting function are known in the art. In U.S. Pat. No. 3,924,421, for example, a cam plate is mounted on a driving member and a driven member is connected to a cam follower on a pivot lever. The follower engages with a seat in the cam under an applied force by a spring acting on the lever. The cam follower moves from the seat of the cam when an overload occurs whereby the driving member rotates relative to the driven member. The cam follower and cam are located in a lubricant-filled cavity formed in a housing which is supported by anti-friction bearings on the driven and driving members.
In U.S. Pat. No. 3,282,387, there is disclosed a detent-type overload clutch having buttonhead plungers engaged with compression springs arranged so that the buttonhead portions of the plungers will move out of conical seats when an overload occurs. The conical seats are formed in a wear plate that abuts against one side of a driven member and coupled thereto by a key or dowel pin. The opposite side of the driven member is engaged by a flange. A detent support plate is connected to the flange by bolts. The detent support plate is connected to a driving member such as a motor. The force of the springs acting on the buttonhead plungers is applied by the flange to a broad surface area of the driven member. The frictional engagement between the flange and the driven member contributes to the torque-transmitting ability by the clutch. The maximum torque the clutch will transmit before disengagement takes place can be changed by changing the spring force and will vary with a change to the coefficient of friction between the flange and driven member due to temperature, humidity, deterioration of the friction surfaces and the like. Thus, erratic changes occur to the value of the maximum torque at which the clutch transmits before disengagement takes place. A detent clutch of this type cannot accommodate relative axial movement between the machine elements to which it is connected. When the possibility of axial movement is excluded by the design of the clutch, it must accommodate forces in an axial direction. These forces are applied in such a way to alter the spring pressure and adversely affect reliance on friction.